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Effect of surface treatment methods on the shear bond strength between resin cement and all-ceramic core materials
Journal of Non-Crystalline Solids 358 (2012) 925–930
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Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/ locate/ jnoncrysol
Effect of surface treatment methods on the shear bond strength between resin cement and all-ceramic core materials Munir Tolga Yucel ⁎, Filiz Aykent, Serhan Akman, Isa Yondem Selcuk University, Faculty of Dentistry, Department of Prosthodontics, Konya, Turkey
a r t i c l e
i n f o
Article history: Received 2 November 2011 Received in revised form 26 December 2011 Available online 24 January 2012 Keywords: Bond strength; Surface treatment; Luting cement; Lithium–disilicate ceramics; Nd:YAG Laser
a b s t r a c t This study compared the influence of various surface treatments on the shear bond strength between resin cement and lithium disilicate glass-ceramics. A series of 120 lithium disilicate ceramic samples were prepared to compare the effect of different surface treatments on the shear strength of a luting cement bonded to two all-ceramic systems. IPS Empress 2 and IPS e.max Press ceramic samples were fabricated according to the manufacturer's instructions. The ceramic samples were divided into the following 6 surface treatment groups for each ceramic system: 1—no treatment (C), 2—airborne-particle abrasion (A), 3—acid etching (E), 4—airborne-particle abrasion + acid etching (AE), 5—Nd:YAG laser (L), 6—Nd:YAG laser + acid etching (LE). Resin cement was then bonded to the treated ceramic surfaces and light polymerized. The shear bond strengths of the specimens were measured using a universal testing machine. Two-way ANOVA and Tukey HSD (α = 0.05) test were used to determine differences in shear bond strength between the groups. The ANOVA revealed significant differences between the treatment groups and ceramic types (p b 0.05). The shear bond strengths of IPS Empress 2 were significantly higher than those of IPS e.max Press. © 2012 Elsevier B.V. All rights reserved.
1. Introduction The increased desire for optimum esthetics in restorative dental treatment has led to the use of all-ceramic crowns as an alternative in both anterior and posterior restorations [1]. The IPS Empress system (Ivoclar-Vivadent) was introduced in 1990 and became a popular all-ceramic system for pressed glass-ceramic inlays, onlays, crowns, and veneers. However, the limited mechanical strength of IPS Empress meant that it could not be used for dental bridges [2,3]. With IPS Empress, 30–40% crystal content can be introduced before the esthetics of the core and resulting restoration are compromised. In IPS Empress 2, controlled crystallization production of a lithium disilicate glass ceramic enables the creation of 60% crystal content (by volume) without loss of translucency, as the refractive index of the crystals is similar to that of the glassy matrix. Furthermore, the strength of the resulting material is reported to be three times that of the original Empress, with a flexural strength of almost 200 MPa [4,5]. In 2005, an improved press ceramic material called IPS e.max Press (Ivoclar-Vivadent) was introduced. This material consists of a lithium disilicate pressed glass-ceramic. The chemical basis of the material is the same as that of IPS Empress 2 (2SiO2–LiO2), but its properties are altered by a different firing process [6–8].
⁎ Corresponding author at: Selcuk University, Faculty of Dentistry, Department of Prosthodontics, Konya, Turkey. Tel.: + 90 332 223 11 94. E-mail address: [email protected] (M.T. Yucel). 0022-3093/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2012.01.006
The bonding of resin composite to ceramic materials plays an important role in dentistry. Resin bonding between a tooth and a restoration is advocated for improving retention, marginal adaptation, and fracture resistance of restorations [9,10]. Achieving adhesion between a luting agent and a ceramic surface requires surface pretreatment [10,11]. A strong resin bond relies on micromechanical interlocking and chemical bonding to the ceramic surface, which requires surface roughening and cleaning for adequate surface activation [12]. Surface treatment of ceramics increases the surface area and creates microporosities on the ceramic surface, which enhance the potential for mechanical retention of the luting composite resin [13]. An increasing number of surface treatment methods are being introduced to create a reliable bond between the ceramic material and adhesive resins [14–21]. Etching the surface of a ceramic restoration with hydrofluoric acid and the application of a silane coupling agent is a well-known and recommended method to increase bond strength [10,17]. Hydrofluoric acid attacks the glass phase, producing a retentive surface for micromechanical bonding. However, an increase in mechanical strength, by increasing the crystalline content and decreasing the glass content, results in an acid-resistant ceramic, whereby any type of acid treatment produces insufficient surface changes for adequate bonding to resin [22]. Another pre-bonding treatment recommended for ceramic surfaces is airborne abrasion by aluminum oxide particles [13,23,24]. Research shows that sandblasting with 50-μm aluminum oxide particles is a better method for preparing the surface than bur-performed restorations. Nevertheless, sandblasting alone is not sufficient to improve the bond of the composite–porcelain interface [25–28].
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Since the development of the ruby laser by Maiman [29] in 1960, lasers have become widely used in medicine and dentistry. The neodymium:yttrium-aluminium-garnet (Nd:YAG) laser was invented in 1961 by Snitzer and then marketed as an instrument for use on both hard and soft dental tissues [30]. Carbon dioxide (CO2) and Nd:YAG lasers are the most generally used instruments for both intraoral soft tissue surgery and hard tissue applications [31]. Lasers have also been used in processing dental materials, especially for fusing materials onto or into tooth surfaces [32]. Relatively few studies have examined the laser treatment of dental ceramic masses [32,33]. Many studies have evaluated the influence of surface treatments on the bond strength of luting agents to dental ceramics [34–40]. However, there is insufficient information about the bond strength of the IPS e.max Press system. Thus, the purpose of this study was to compare the influence of various surface treatments on the shear bond strength between resin cement and two lithium disilicate ceramics. The null hypothesis was that Nd:YAG laser treatment would not increase surface roughness and bond strength more than the other surface treatment methods. 2. Materials and methods A total of 120 lithium–disilicate ceramic samples were prepared to compare the effect of different surface treatments on the shear strength of luting cement bonding to two types of all-ceramic systems. IPS Empress 2 and IPS e.max Press ceramic were used to fabricate 60 ceramic blocks each (10 × 10 × 2 mm). Ceramic specimens of each core material were fabricated following the manufacturers’ instructions. All 120 ceramic blocks were embedded in chemically cured acrylic resin (Meliodent; Bayer Dental Ltd., Newbury, UK). The surface of each sample was ground with a series of siliconcarbide abrasive papers to obtain a smooth surface (300, 400, 600, 800 and 1000 grit) and cleaned for 10 minutes in an ultrasonic cleaner (Whaledent Biosonic, Whaledent Inc., New York, USA). 2.1. Surface treatment methods The two types ceramic blocks were divided into 6 subgroups that received different surface treatments for each ceramic system. Group 1 (C): No surface treatment (as control). Group 2 (A): Airborne-particle abrasion Group 3 (E): Etching Group 4 (AE): Airborne-particle abrasion and etching Group 5 (L): Laser (Nd:YAG) Group 6 (LE): Laser and Etching
electron microscope (SEM) (LEO 440, Electron Microscopy Ltd., Cambridge, UK) at 20 kV (1000× magnification). 2.3. Bonding, thermocycling, and testing procedures All ceramic samples were air-dried and coated with a silane coupling agent (Monobond-S; Ivoclar Vivadent, Schaan, Lichtenstein). Teflon tubes (5 mm in diameter and 4 mm in height) were used to fabricate standardized resin cylinders. The low-viscous resin cement (Variolink II, Ivoclar Vivadent, Schaan, Lichtenstein) was then bonded to the treated ceramic surfaces using a composite-filling instrument according to the manufacturer's recommendations and then light polymerized for 40 seconds with a light curing unit (Blue Swan, Dentanet, Istanbul, Turkey). Light intensity was at least 650 mW/cm2. Teflon molds were gently removed from the samples. The entire surface of the resin cement cylinder was light-cured for a total of 80 seconds. The specimens were then thermocycled for 2000 cycles between 5 °C and 55 °C with a dwell time of 25 seconds before testing. The shear bond strengths of the specimens were measured using a universal testing machine at a crosshead speed of 0.5 mm/min (Fig. 1). Shear load at failure was recorded. 2.4. Statistical analysis Two-way analysis of variance (ANOVA) and Tukey HSD tests were used to determine differences in shear bond strength values between the groups (SPSS, Chicago, IL). 3. Results The mean and standard deviation for all surface treatment groups are listed in Table 1 and illustrated in Fig. 2. ANOVA revealed significant differences between the treatment groups and ceramics (p b 0.05) (Table 2). The mean shear bond strength values of IPS Empress 2 were significantly higher than in IPS e.max Press. The acid etch groups had significantly higher mean values (p b 0.05) than the other groups. Laser groups showed significantly lower shear bond strength values than the other treatments. For both ceramics, the control groups showed significantly lower shear bond strength values than the other groups. Etching after airborne-particle abrasion showed the highest shear bond strength values for both the e.max Press and Empress 2 samples. SEM evaluation of treated surfaces of the samples is shown in Figs. 3 and 4, respectively. The SEM images of the laser irradiation surfaces appeared relatively smooth compared with the images of
For airborne-particle abrasion groups; 50-μm aluminum oxide was used as an abrasive material at a pressure of 40 psi (Bego EasyBlast, Bego, Bremen, Germany) from a distance of approximately 10 mm for 5 seconds. For hydrofluoric acid-etched groups; the ceramic samples were etched with 4.9% hydrofluoric acid gel (IPS Ceramic etching gel, Ivoclar Vivadent, Schaan, Lichtenstein) for 20 seconds. In the laser groups, an Nd:YAG laser (DEKA M.E.L.A., Calenzano, Italy) was used for laser irradiation of the ceramic surfaces. The laser optical fiber (300 μm in diameter) was aligned perpendicular to the ceramic surface at 1 mm distance and scanned the whole ceramic area. The laser parameters used were 100 mJ (pulse energy), 20 Hz (pulses per second), 2 W (power setting), 141.54 J/cm 2 (energy density), and 150 μs (pulse duration) [41]. The prepared surfaces were cleaned ultrasonically for 30 minutes. 2.2. SEM evaluation For micromorphological examination of ceramic surfaces, one additional specimen from each group was analyzed using a scanning
Fig. 1. Schematic diagram of shear testing.
M.T. Yucel et al. / Journal of Non-Crystalline Solids 358 (2012) 925–930 Table 1 Mean values and standard deviations of the groups (MPa).
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Table 2 Results of two-way analysis of variance (p b 0.05).
Schematic diagram of shear testing
Schematic diagram of shear testing
Schematic diagram of shear testing
C A E AE L LE
7.5 ± 1.4a 17.7 ± 0.9b 22.1 ± 3.4c 28.2 ± 1.9d 11.9 ± 0.9e 23.7 ± 2.2c
12.6 ± 1.8a 20.5 ± 1.3b 25.9 ± 2.1c 30.2 ± 2d 15.6 ± 2e 27.4 ± 3.1c
C: control, A: Airborne-particle abrasion, E: etching, L: Laser. a-e For each vertical column; Statistically different from each other (p b 0.05).
other treated groups. Hydrofluoric acid etching of both ceramic groups produced elongated crystals with shallow irregularities. Airborne particle abrasion with 50-μm aluminum oxide modified the surface morphology of both ceramic groups.
4. Discussion This study was designed to investigate the influence of different surface treatments on the shear bond strength of a dual-cure resin cement to lithium disilicate ceramics cores. The micromechanical retention of the ceramic surface is very important for bonding with a resin luting cement. Resin luting agents are dependent on micromechanical retention for bonding [13]. The unfilled resin and the resin luting cement are applied to the treated ceramic surface. This penetration and in situ polymerization is responsible for the bonding of the resin luting agent to the ceramic restoration [1,20,35,38]. Etching porcelain and pressed glass-ceramic surfaces with hydrofluoric acid is an established method of increasing bond strength [34–36]. This process results in higher surface roughness and increased surface area, which provide increased physical interaction and improved mechanical retention with the cementing agents [36,37]. Airborne particle abrasion with aluminum oxide is another method of surface roughening [17,20,34]. In the present study, airborne particle abrasion was performed with 50-μm aluminum oxide particles at a pressure of 40 psi for 5 seconds. For both ceramic groups, this treatment changed the surface by increasing the number of pits per unit area compared with the control group. The application of a silane coupling agent to the pre-treated ceramic surface provides a chemical covalent and hydrogen bond of
Fig. 2. Mean shear bond strength (MPa) and standard deviation of each of the groups.
Source
df
Ceramic type (A) 1 Surface conditioning (B) 5 A*B 5 Error 108 Total 120
Sum of squares Mean square F-value 373.439 5396.714 28.113 456.823 55638.921
373.439 1079.343 5.623 4.230
P value
88.287 0.000 255.173 0.000 1.329 0.257
resin systems to ceramic and is a significant factor in achieving a sufficient resin bond to silica-based ceramics [15–17,20,34,37]. The results of this study showed that only airborne-particle abrasion was less effective than the combination of etching and airborneparticle abrasion procedure. In both ceramic groups, when single procedures were used alone, the etching procedure was found to be most effective. The opacity of ceramics is controlled by the nanostructure of the material. Scattering of light at the interfaces between the crystals and the glass matrix causes a higher opacity. If there is a similar refractive index of light between the crystals and the glass matrix, such as between the lithium disilicate crystals and the glass matrix, it is possible to achieve a very high translucency. If the refractive index between the crystals and the glass is high, then higher opacity results, as with nano crystals included for the high-opacity materials. Thus, the opacity may be tailored for a variety of different applications, to produce translucencies that are well accepted within the industry [42]. In the present study, IPS Empress 2 was found to have significantly higher shear bond strength than IPS e.max Press. The significant difference in bond strength of resin cement to the cores after various treatments might also be explained by the differences in microstructure of IPS e.max that were used to improve the esthetics. SEM examination showed the difference between the crystal sizes of the etched IPS Empress 2 and IPS e.max Press ceramics (Fig. 5). Nano crystals may affect the bond strength of resin cement to ceramic cores. In the present study, 2 W output power (100 mJ = pulse at 20 Hz) was used for laser irradiation. SEM analysis revealed that the Nd:YAG laser did not effectively change the surface structure of the ceramics. The present study showed that shear bond strength after hydrofluoric acid etching is more effective than Nd:YAG laser etching. SEM analysis revealed that, when hydrofluoric acid was applied after laser irradiation, the fissures and cracks were larger than seen on the laser-irradiated surfaces. Continuous developments have been made in laser technology in order to reduce heat-related structural changes and damage to surrounding dental tissues. There are currently more than 10 different laser types used in research into their effects on dental hard tissues and dental materials. The CO2 laser is well suited to the treatment of ceramic materials, since its emission wavelength is almost entirely absorbed by ceramics [39]. One of the limitations of the present study is that only an Nd:YAG laser was used for surface treatment and different power settings were not used for laser irradiation. Further studies are needed to compare the efficiency of laser systems on surface treatments. Another limitation of the present study is that only one luting agent was used on the treated surfaces. According to Höland et al. [3], the main crystal phase of IPS Empress 2 glassceramic consists of elongated crystals of lithium disilicate; a second phase is composed of lithium orthophosphate; and a glass matrix surrounds both crystalline phases. Hydrofluoric acid is able to remove the glass matrix and the second crystalline phase, thus creating irregularities within the lithium disilicate crystals [13]. The present study shows that etching with 4.9% hydrofluoric acid for 20 seconds on IPS Empress 2 and IPS e.max Press ceramics is effective in the removal of the glass matrix and therefore creates a suitable surface for bonding to lithium disilicate cores. %4,9 hydrofluoric acid etching changed
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Fig. 3. SEM images of IPS Empress 2 surfaces: A Control; B Airborne-particle abrasion; C Nd:YAG Laser; D Hydrofluoric acid etch; E Laser + etch; F Airborne-particle abrasion + Etch (original magnification 1000×).
the morphologic surface of IPS Empress 2 and IPS e.max Press ceramics. After surface treatment, elongated crystals and shallow irregularities were clearly observed. Silane treatment has been demonstrated to be essential to achieving chemical adhesion between the ceramic and resin cement, but the possible effect of thermocycling in weakening the silane bond after hydrofluoric acid etching should be considered. Thermocycling has a
significant effect on bond strength; bond strength values were reported to be lower compared to cases where no thermocycling was applied [10]. In the present study, the specimens were thermocycled for 2000 cycles and then a common shear bond strength test was used to reflect the clinical situation. This study revealed a strong relationship between surface roughness and shear bond strength for lithium–disilicate ceramics.
Fig. 4. SEM images of IPS e.max Press surfaces: A Control; B Airborne-particle abrasion; C Nd:YAG Laser; D Hydrofluoric acid etch; E Laser + etch; F Airborne-particle abrasion + Etch (original magnification 1000 ×).
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Fig. 5. SEM images of lithium disilicate crystals after etching: A IPS Empress 2; B IPS e.max Press (original magnification 5000 ×).
5. Conclusions Within the limitations of this in vitro study, the following conclusions were drawn: 1. IPS Empress 2 ceramic cores showed significantly higher shear bond strength values than IPS e.max Press. 2. Shear bond strengths were significantly affected by surface treatments. 3. The micromorphology of ceramic surfaces after Nd:YAG laser irradiation was similar to the surfaces of untreated ceramics. 4. This in vitro study demonstrated that etching was necessary to obtain a strong shear bond between resin cement and lithium disilicate cores. 6. Conflict of interest statement The authors declare that they have no financial, professional, or other personal interest that could influence the position presented in the paper. Acknowledgements This study was funded by the Research Projects Council of the University of Selcuk, Turkey. References [1] W. Awliya, A. Oden, P. Yaman, J.B. Dennison, M.E. Razzoog, Shear bond strength of a resin cement to densely sintered high-purity alumina with various surface conditions, Acta Odontol. Scand. 56 (1998) 9–13. [2] S. Wolfart, F. Bohlsen, S.M. Wegner, M. Kern, A preliminary prospective evaluation of all-ceramic crown-retained and inlay-retained fixed partial dentures, Int. J. Prosthodont. 18 (2005) 497–505. [3] W. Höland, M. Schweiger, M. Frank, V. Rheinberger, A comparison of the microstructure and properties of the IPS Empress 2 and the IPS Empress glassceramics, J. Biomed. Mater. Res. Appl. Biomater. 53 (2000) 297–303. [4] J.A. Sorensen, M. Cruz, W.T. Mito, Research evaluations of a lithium disilicate restorative system, Empress 2 Signature Int. 5 (1998) 4–10. [5] A.J.E. Qualtrough, V. Piddock, Dental ceramics: what's new? Dent. Update 29 (2002) 25–33. [6] C.F. Stappert, N. Stathopoulou, T. Gerds, J.R. Strub, Survival rate and fracture strength of maxillary incisors, restored with different kinds of full veneers, J. Oral Rehabil. 32 (2005) 266–272. [7] C.F. Stappert, W. Att, T. Gerds, J.R. Strub, Fracture resistance of different partialcoverage ceramic molar restorations, J. Am. Dent. Assoc. 137 (2006) 514–522. [8] C.F. Stappert, N. Denner, T. Gerds, J.R. Strub, Marginal adaptation of different types of all-ceramic partial coverage restorations after exposure to an artificial mouth, Br. Dent. J. 199 (2005) 779–783. [9] M.F. Ayad, N.Z. Fahmy, S.F. Rosenstiel, Effect of surface treatment on roughness and bond strength of a heat-pressed ceramic, J. Prosthet. Dent. 99 (2008) 123–130. [10] M. Ozcan, P.K. Vallittu, Effect of surface conditioning methods on the bond strength of luting cement to ceramics, Dent. Mater. 19 (2003) 725–731. [11] M. Ozcan, The use of chairside silica coating for different dental applications: a clinical report, J. Prosthet. Dent. 87 (2002) 469–472. [12] M.B. Blatz, A. Sadan, M. Kern, Resin-ceramic bonding: a review of the literature, J. Prosthet. Dent. 89 (2003) 268–274.
[13] G.A. Borges, A.M. Sophr, M.F. Goes, L.C. Sobrinho, C.N. Daniel, Effect of etching and airborne particle abrasion on the microstructure of different dental ceramics, J. Prosthet. Dent. 89 (2003) 479–488. [14] G. Saygılı, S. Şahmalı, Effect of ceramic surface treatment on the shear bond strengths of two resin luting agents to all-ceramic materials, J. Oral Rehabil. 30 (2003) 758–764. [15] H.R. Horn, Porcelain laminate veneers bonded to etched enamel, Dent. Clin. North Am. 27 (1983) 671–684. [16] A.H. Suliman, J.S. Edward, P. Jorge, Effect of surface treatment and bonding agents on bond strength of composite resin to porcelain, J. Prosthet. Dent. 70 (1993) 118–120. [17] M. Aida, T. Hayakawa, K. Mizukawa, Adhesion of composite to porcelain with various surface conditions, J. Prosthet. Dent. 73 (1995) 464–470. [18] A.M. Lacy, J. La Luz, L.G. Watanabe, M. Dellinges, Effect of porcelain surface treatment on the bond to composite, J. Prosthet. Dent. 60 (1988) 288–291. [19] A.N. Ozden, F. Akaltan, G. Can, Effect of surface treatments of porcelain on the shear bond strength of applied dual-cured cement, J. Prosthet. Dent. 72 (1994) 85–88. [20] K. Kamada, K. Yoshida, M. Atsuta, Effect of ceramic surface treatments on the bond of four resin luting agents to a ceramic material, J. Prosthet. Dent. 79 (1998) 508–513. [21] N. Madani, F.C.S. Chu, A.V. McDonald, R.J. Smales, Effects of surface treatments on shear bond strengths between a resin cement and an alumina core, J. Prosthet. Dent. 83 (2000) 644–647. [22] A. Della Bona, Characterizing ceramics and the interfacial adhesion to resin: II— the relationship of surface treatment, bond strength, interfacial toughness and fractography, J. Appl. Oral Sci. 13 (2005) 101–109. [23] H. Kato, H. Matsumura, M. Atsuta, Effect of etching and sandblasting on bond strength to sintered porcelain of unfilled resin, J. Oral Rehabil. 27 (2000) 103–110. [24] D. Sen, E. Poyrazoglu, B. Tuncelli, G. Goller, Shear bond strength of resin luting cement to glass-infiltrated porous aluminum oxide cores, J. Prosthet. Dent. 83 (2000) 210–215. [25] D.M. Wolf, J.M. Powres, K.L. O'Keefe, Bond strength of composite to etched and sandblasted porcelain, Am. J. Dent. 6 (1993) 155–158. [26] W.P. Kelsey, M.A. Latta, C.M. Stanislav, R.S. Shaddy, Comparison of composite resin-to-porcelain bond strength with three adhesives, Gen. Dent. 48 (2000) 418–421. [27] K.A. Kupiec, K.M. Wuertz, W.W. Barkmeier, T.M. Wilweding, Evaluation of porcelain surface treatment and agents for composite porcelain repair, J. Prosthet. Dent. 76 (1996) 119–124. [28] C.M. Kussano, G. Bonfante, J.G. Batista, J.H.N. Pinto, Evaluation of shear bond strength of composite to porcelain according to surface treatment, Braz. Dent. J. 14 (2003) 132–135. [29] T.H. Maiman, Stimulated optical radiation in ruby, Nature 187 (1960) 493. [30] L.J. Miserendino, The history and development of laser dentistry, in: L.J. Miserendino, R.M. Pick (Eds.), Laser in Dentistry, 1st ed., Quintessence Publishing Co.,Inc., Singapore, 1995, p. 17. [31] R.A. Convissar, E.E. Goldstein, A combined carbon dioxide/erbium laser for soft and hard tissue procedures, Dent. Today 20 (2001) 66–71. [32] E. Beyer, K. Behter, U. Petschke, Schweissen mit CO2-Lasern, Laser u Optoelektronik 18 (1986) 35–46.Misrendino LJ, Pick RM, editors. Lasers in dentistry. Chicago: Quintessence;. p. 231–245 [33] T. Akova, O. Yoldas, M.S. Toroglu, H. Uysal, Porcelain surface treatment by laser for bracket-porcelain bonding, Am. J. Orthod. Dentofacial Orthop. 128 (2005) 630–637. [34] J.W. Thurmond, W.W. Barkmeier, T.M. Wilwerding, Effect of porcelain surface treatments on bond strengths of composite resin bonded to porcelain, J. Prosthet. Dent. 72 (1994) 355–359. [35] I. Stangel, D. Nathanson, C.S. Hsu, Shear strength of the composite bond to etched porcelain, J. Dental Res. 66 (1987) 1460–1465. [36] A. Piwowarczyk, H.C. Hauer, J.A. Sorensen, In vitro shear bond strength of cementing agents to fixed prosthodontic restorative materials, J. Prosthet. Dent. 92 (2004) 265–273. [37] A. Della Bona, K.J. Anusavice, C. Shen, Microtensile strength of composite bonded to hot-pressed ceramics, J. Adhes. Dent. 2 (2000) 305–313.
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[38] M. Ozcan, H.N. Alkumru, D. Gemalmaz, The effect of surface treatment on the shear bond strength of luting cement to a glass-infiltrated alumina ceramic, Int. J. Prosthodont. 14 (2001) 335–339. [39] B. Gökçe, B. Ozpinar, M. Dündar, E. Cömlekoglu, B.H. Sen, M.A. Güngör, Bond strengths of all-ceramics: acid vs laser etching, Oper. Dent. 32 (2007) 173–178. [40] B. Kim, H.E.K. Bae, J.S. Shim, K.W. Lee, The influence of ceramic surface treatments on the tensile bond strength of composite resin to all-ceramic coping materials, J. Prosthet. Dent. 94 (2005) 357–362.
[41] E. Osorio, M. Toledano, B.L. Silveira, R. Osorio, Effect of different surface treatments on In-Ceram Alumina roughness. An AFM study, J Dent. 38 (2009) 118–122. [42] IPS e.max lithium disilicate; The future of all-ceramic dentistry. Ivoclar-Vivadent documentation, 2009.
Contents lists available at SciVerse ScienceDirect
Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/ locate/ jnoncrysol
Effect of surface treatment methods on the shear bond strength between resin cement and all-ceramic core materials Munir Tolga Yucel ⁎, Filiz Aykent, Serhan Akman, Isa Yondem Selcuk University, Faculty of Dentistry, Department of Prosthodontics, Konya, Turkey
a r t i c l e
i n f o
Article history: Received 2 November 2011 Received in revised form 26 December 2011 Available online 24 January 2012 Keywords: Bond strength; Surface treatment; Luting cement; Lithium–disilicate ceramics; Nd:YAG Laser
a b s t r a c t This study compared the influence of various surface treatments on the shear bond strength between resin cement and lithium disilicate glass-ceramics. A series of 120 lithium disilicate ceramic samples were prepared to compare the effect of different surface treatments on the shear strength of a luting cement bonded to two all-ceramic systems. IPS Empress 2 and IPS e.max Press ceramic samples were fabricated according to the manufacturer's instructions. The ceramic samples were divided into the following 6 surface treatment groups for each ceramic system: 1—no treatment (C), 2—airborne-particle abrasion (A), 3—acid etching (E), 4—airborne-particle abrasion + acid etching (AE), 5—Nd:YAG laser (L), 6—Nd:YAG laser + acid etching (LE). Resin cement was then bonded to the treated ceramic surfaces and light polymerized. The shear bond strengths of the specimens were measured using a universal testing machine. Two-way ANOVA and Tukey HSD (α = 0.05) test were used to determine differences in shear bond strength between the groups. The ANOVA revealed significant differences between the treatment groups and ceramic types (p b 0.05). The shear bond strengths of IPS Empress 2 were significantly higher than those of IPS e.max Press. © 2012 Elsevier B.V. All rights reserved.
1. Introduction The increased desire for optimum esthetics in restorative dental treatment has led to the use of all-ceramic crowns as an alternative in both anterior and posterior restorations [1]. The IPS Empress system (Ivoclar-Vivadent) was introduced in 1990 and became a popular all-ceramic system for pressed glass-ceramic inlays, onlays, crowns, and veneers. However, the limited mechanical strength of IPS Empress meant that it could not be used for dental bridges [2,3]. With IPS Empress, 30–40% crystal content can be introduced before the esthetics of the core and resulting restoration are compromised. In IPS Empress 2, controlled crystallization production of a lithium disilicate glass ceramic enables the creation of 60% crystal content (by volume) without loss of translucency, as the refractive index of the crystals is similar to that of the glassy matrix. Furthermore, the strength of the resulting material is reported to be three times that of the original Empress, with a flexural strength of almost 200 MPa [4,5]. In 2005, an improved press ceramic material called IPS e.max Press (Ivoclar-Vivadent) was introduced. This material consists of a lithium disilicate pressed glass-ceramic. The chemical basis of the material is the same as that of IPS Empress 2 (2SiO2–LiO2), but its properties are altered by a different firing process [6–8].
⁎ Corresponding author at: Selcuk University, Faculty of Dentistry, Department of Prosthodontics, Konya, Turkey. Tel.: + 90 332 223 11 94. E-mail address: [email protected] (M.T. Yucel). 0022-3093/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2012.01.006
The bonding of resin composite to ceramic materials plays an important role in dentistry. Resin bonding between a tooth and a restoration is advocated for improving retention, marginal adaptation, and fracture resistance of restorations [9,10]. Achieving adhesion between a luting agent and a ceramic surface requires surface pretreatment [10,11]. A strong resin bond relies on micromechanical interlocking and chemical bonding to the ceramic surface, which requires surface roughening and cleaning for adequate surface activation [12]. Surface treatment of ceramics increases the surface area and creates microporosities on the ceramic surface, which enhance the potential for mechanical retention of the luting composite resin [13]. An increasing number of surface treatment methods are being introduced to create a reliable bond between the ceramic material and adhesive resins [14–21]. Etching the surface of a ceramic restoration with hydrofluoric acid and the application of a silane coupling agent is a well-known and recommended method to increase bond strength [10,17]. Hydrofluoric acid attacks the glass phase, producing a retentive surface for micromechanical bonding. However, an increase in mechanical strength, by increasing the crystalline content and decreasing the glass content, results in an acid-resistant ceramic, whereby any type of acid treatment produces insufficient surface changes for adequate bonding to resin [22]. Another pre-bonding treatment recommended for ceramic surfaces is airborne abrasion by aluminum oxide particles [13,23,24]. Research shows that sandblasting with 50-μm aluminum oxide particles is a better method for preparing the surface than bur-performed restorations. Nevertheless, sandblasting alone is not sufficient to improve the bond of the composite–porcelain interface [25–28].
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Since the development of the ruby laser by Maiman [29] in 1960, lasers have become widely used in medicine and dentistry. The neodymium:yttrium-aluminium-garnet (Nd:YAG) laser was invented in 1961 by Snitzer and then marketed as an instrument for use on both hard and soft dental tissues [30]. Carbon dioxide (CO2) and Nd:YAG lasers are the most generally used instruments for both intraoral soft tissue surgery and hard tissue applications [31]. Lasers have also been used in processing dental materials, especially for fusing materials onto or into tooth surfaces [32]. Relatively few studies have examined the laser treatment of dental ceramic masses [32,33]. Many studies have evaluated the influence of surface treatments on the bond strength of luting agents to dental ceramics [34–40]. However, there is insufficient information about the bond strength of the IPS e.max Press system. Thus, the purpose of this study was to compare the influence of various surface treatments on the shear bond strength between resin cement and two lithium disilicate ceramics. The null hypothesis was that Nd:YAG laser treatment would not increase surface roughness and bond strength more than the other surface treatment methods. 2. Materials and methods A total of 120 lithium–disilicate ceramic samples were prepared to compare the effect of different surface treatments on the shear strength of luting cement bonding to two types of all-ceramic systems. IPS Empress 2 and IPS e.max Press ceramic were used to fabricate 60 ceramic blocks each (10 × 10 × 2 mm). Ceramic specimens of each core material were fabricated following the manufacturers’ instructions. All 120 ceramic blocks were embedded in chemically cured acrylic resin (Meliodent; Bayer Dental Ltd., Newbury, UK). The surface of each sample was ground with a series of siliconcarbide abrasive papers to obtain a smooth surface (300, 400, 600, 800 and 1000 grit) and cleaned for 10 minutes in an ultrasonic cleaner (Whaledent Biosonic, Whaledent Inc., New York, USA). 2.1. Surface treatment methods The two types ceramic blocks were divided into 6 subgroups that received different surface treatments for each ceramic system. Group 1 (C): No surface treatment (as control). Group 2 (A): Airborne-particle abrasion Group 3 (E): Etching Group 4 (AE): Airborne-particle abrasion and etching Group 5 (L): Laser (Nd:YAG) Group 6 (LE): Laser and Etching
electron microscope (SEM) (LEO 440, Electron Microscopy Ltd., Cambridge, UK) at 20 kV (1000× magnification). 2.3. Bonding, thermocycling, and testing procedures All ceramic samples were air-dried and coated with a silane coupling agent (Monobond-S; Ivoclar Vivadent, Schaan, Lichtenstein). Teflon tubes (5 mm in diameter and 4 mm in height) were used to fabricate standardized resin cylinders. The low-viscous resin cement (Variolink II, Ivoclar Vivadent, Schaan, Lichtenstein) was then bonded to the treated ceramic surfaces using a composite-filling instrument according to the manufacturer's recommendations and then light polymerized for 40 seconds with a light curing unit (Blue Swan, Dentanet, Istanbul, Turkey). Light intensity was at least 650 mW/cm2. Teflon molds were gently removed from the samples. The entire surface of the resin cement cylinder was light-cured for a total of 80 seconds. The specimens were then thermocycled for 2000 cycles between 5 °C and 55 °C with a dwell time of 25 seconds before testing. The shear bond strengths of the specimens were measured using a universal testing machine at a crosshead speed of 0.5 mm/min (Fig. 1). Shear load at failure was recorded. 2.4. Statistical analysis Two-way analysis of variance (ANOVA) and Tukey HSD tests were used to determine differences in shear bond strength values between the groups (SPSS, Chicago, IL). 3. Results The mean and standard deviation for all surface treatment groups are listed in Table 1 and illustrated in Fig. 2. ANOVA revealed significant differences between the treatment groups and ceramics (p b 0.05) (Table 2). The mean shear bond strength values of IPS Empress 2 were significantly higher than in IPS e.max Press. The acid etch groups had significantly higher mean values (p b 0.05) than the other groups. Laser groups showed significantly lower shear bond strength values than the other treatments. For both ceramics, the control groups showed significantly lower shear bond strength values than the other groups. Etching after airborne-particle abrasion showed the highest shear bond strength values for both the e.max Press and Empress 2 samples. SEM evaluation of treated surfaces of the samples is shown in Figs. 3 and 4, respectively. The SEM images of the laser irradiation surfaces appeared relatively smooth compared with the images of
For airborne-particle abrasion groups; 50-μm aluminum oxide was used as an abrasive material at a pressure of 40 psi (Bego EasyBlast, Bego, Bremen, Germany) from a distance of approximately 10 mm for 5 seconds. For hydrofluoric acid-etched groups; the ceramic samples were etched with 4.9% hydrofluoric acid gel (IPS Ceramic etching gel, Ivoclar Vivadent, Schaan, Lichtenstein) for 20 seconds. In the laser groups, an Nd:YAG laser (DEKA M.E.L.A., Calenzano, Italy) was used for laser irradiation of the ceramic surfaces. The laser optical fiber (300 μm in diameter) was aligned perpendicular to the ceramic surface at 1 mm distance and scanned the whole ceramic area. The laser parameters used were 100 mJ (pulse energy), 20 Hz (pulses per second), 2 W (power setting), 141.54 J/cm 2 (energy density), and 150 μs (pulse duration) [41]. The prepared surfaces were cleaned ultrasonically for 30 minutes. 2.2. SEM evaluation For micromorphological examination of ceramic surfaces, one additional specimen from each group was analyzed using a scanning
Fig. 1. Schematic diagram of shear testing.
M.T. Yucel et al. / Journal of Non-Crystalline Solids 358 (2012) 925–930 Table 1 Mean values and standard deviations of the groups (MPa).
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Table 2 Results of two-way analysis of variance (p b 0.05).
Schematic diagram of shear testing
Schematic diagram of shear testing
Schematic diagram of shear testing
C A E AE L LE
7.5 ± 1.4a 17.7 ± 0.9b 22.1 ± 3.4c 28.2 ± 1.9d 11.9 ± 0.9e 23.7 ± 2.2c
12.6 ± 1.8a 20.5 ± 1.3b 25.9 ± 2.1c 30.2 ± 2d 15.6 ± 2e 27.4 ± 3.1c
C: control, A: Airborne-particle abrasion, E: etching, L: Laser. a-e For each vertical column; Statistically different from each other (p b 0.05).
other treated groups. Hydrofluoric acid etching of both ceramic groups produced elongated crystals with shallow irregularities. Airborne particle abrasion with 50-μm aluminum oxide modified the surface morphology of both ceramic groups.
4. Discussion This study was designed to investigate the influence of different surface treatments on the shear bond strength of a dual-cure resin cement to lithium disilicate ceramics cores. The micromechanical retention of the ceramic surface is very important for bonding with a resin luting cement. Resin luting agents are dependent on micromechanical retention for bonding [13]. The unfilled resin and the resin luting cement are applied to the treated ceramic surface. This penetration and in situ polymerization is responsible for the bonding of the resin luting agent to the ceramic restoration [1,20,35,38]. Etching porcelain and pressed glass-ceramic surfaces with hydrofluoric acid is an established method of increasing bond strength [34–36]. This process results in higher surface roughness and increased surface area, which provide increased physical interaction and improved mechanical retention with the cementing agents [36,37]. Airborne particle abrasion with aluminum oxide is another method of surface roughening [17,20,34]. In the present study, airborne particle abrasion was performed with 50-μm aluminum oxide particles at a pressure of 40 psi for 5 seconds. For both ceramic groups, this treatment changed the surface by increasing the number of pits per unit area compared with the control group. The application of a silane coupling agent to the pre-treated ceramic surface provides a chemical covalent and hydrogen bond of
Fig. 2. Mean shear bond strength (MPa) and standard deviation of each of the groups.
Source
df
Ceramic type (A) 1 Surface conditioning (B) 5 A*B 5 Error 108 Total 120
Sum of squares Mean square F-value 373.439 5396.714 28.113 456.823 55638.921
373.439 1079.343 5.623 4.230
P value
88.287 0.000 255.173 0.000 1.329 0.257
resin systems to ceramic and is a significant factor in achieving a sufficient resin bond to silica-based ceramics [15–17,20,34,37]. The results of this study showed that only airborne-particle abrasion was less effective than the combination of etching and airborneparticle abrasion procedure. In both ceramic groups, when single procedures were used alone, the etching procedure was found to be most effective. The opacity of ceramics is controlled by the nanostructure of the material. Scattering of light at the interfaces between the crystals and the glass matrix causes a higher opacity. If there is a similar refractive index of light between the crystals and the glass matrix, such as between the lithium disilicate crystals and the glass matrix, it is possible to achieve a very high translucency. If the refractive index between the crystals and the glass is high, then higher opacity results, as with nano crystals included for the high-opacity materials. Thus, the opacity may be tailored for a variety of different applications, to produce translucencies that are well accepted within the industry [42]. In the present study, IPS Empress 2 was found to have significantly higher shear bond strength than IPS e.max Press. The significant difference in bond strength of resin cement to the cores after various treatments might also be explained by the differences in microstructure of IPS e.max that were used to improve the esthetics. SEM examination showed the difference between the crystal sizes of the etched IPS Empress 2 and IPS e.max Press ceramics (Fig. 5). Nano crystals may affect the bond strength of resin cement to ceramic cores. In the present study, 2 W output power (100 mJ = pulse at 20 Hz) was used for laser irradiation. SEM analysis revealed that the Nd:YAG laser did not effectively change the surface structure of the ceramics. The present study showed that shear bond strength after hydrofluoric acid etching is more effective than Nd:YAG laser etching. SEM analysis revealed that, when hydrofluoric acid was applied after laser irradiation, the fissures and cracks were larger than seen on the laser-irradiated surfaces. Continuous developments have been made in laser technology in order to reduce heat-related structural changes and damage to surrounding dental tissues. There are currently more than 10 different laser types used in research into their effects on dental hard tissues and dental materials. The CO2 laser is well suited to the treatment of ceramic materials, since its emission wavelength is almost entirely absorbed by ceramics [39]. One of the limitations of the present study is that only an Nd:YAG laser was used for surface treatment and different power settings were not used for laser irradiation. Further studies are needed to compare the efficiency of laser systems on surface treatments. Another limitation of the present study is that only one luting agent was used on the treated surfaces. According to Höland et al. [3], the main crystal phase of IPS Empress 2 glassceramic consists of elongated crystals of lithium disilicate; a second phase is composed of lithium orthophosphate; and a glass matrix surrounds both crystalline phases. Hydrofluoric acid is able to remove the glass matrix and the second crystalline phase, thus creating irregularities within the lithium disilicate crystals [13]. The present study shows that etching with 4.9% hydrofluoric acid for 20 seconds on IPS Empress 2 and IPS e.max Press ceramics is effective in the removal of the glass matrix and therefore creates a suitable surface for bonding to lithium disilicate cores. %4,9 hydrofluoric acid etching changed
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Fig. 3. SEM images of IPS Empress 2 surfaces: A Control; B Airborne-particle abrasion; C Nd:YAG Laser; D Hydrofluoric acid etch; E Laser + etch; F Airborne-particle abrasion + Etch (original magnification 1000×).
the morphologic surface of IPS Empress 2 and IPS e.max Press ceramics. After surface treatment, elongated crystals and shallow irregularities were clearly observed. Silane treatment has been demonstrated to be essential to achieving chemical adhesion between the ceramic and resin cement, but the possible effect of thermocycling in weakening the silane bond after hydrofluoric acid etching should be considered. Thermocycling has a
significant effect on bond strength; bond strength values were reported to be lower compared to cases where no thermocycling was applied [10]. In the present study, the specimens were thermocycled for 2000 cycles and then a common shear bond strength test was used to reflect the clinical situation. This study revealed a strong relationship between surface roughness and shear bond strength for lithium–disilicate ceramics.
Fig. 4. SEM images of IPS e.max Press surfaces: A Control; B Airborne-particle abrasion; C Nd:YAG Laser; D Hydrofluoric acid etch; E Laser + etch; F Airborne-particle abrasion + Etch (original magnification 1000 ×).
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Fig. 5. SEM images of lithium disilicate crystals after etching: A IPS Empress 2; B IPS e.max Press (original magnification 5000 ×).
5. Conclusions Within the limitations of this in vitro study, the following conclusions were drawn: 1. IPS Empress 2 ceramic cores showed significantly higher shear bond strength values than IPS e.max Press. 2. Shear bond strengths were significantly affected by surface treatments. 3. The micromorphology of ceramic surfaces after Nd:YAG laser irradiation was similar to the surfaces of untreated ceramics. 4. This in vitro study demonstrated that etching was necessary to obtain a strong shear bond between resin cement and lithium disilicate cores. 6. Conflict of interest statement The authors declare that they have no financial, professional, or other personal interest that could influence the position presented in the paper. Acknowledgements This study was funded by the Research Projects Council of the University of Selcuk, Turkey. References [1] W. Awliya, A. Oden, P. Yaman, J.B. Dennison, M.E. Razzoog, Shear bond strength of a resin cement to densely sintered high-purity alumina with various surface conditions, Acta Odontol. Scand. 56 (1998) 9–13. [2] S. Wolfart, F. Bohlsen, S.M. Wegner, M. Kern, A preliminary prospective evaluation of all-ceramic crown-retained and inlay-retained fixed partial dentures, Int. J. Prosthodont. 18 (2005) 497–505. [3] W. Höland, M. Schweiger, M. Frank, V. Rheinberger, A comparison of the microstructure and properties of the IPS Empress 2 and the IPS Empress glassceramics, J. Biomed. Mater. Res. Appl. Biomater. 53 (2000) 297–303. [4] J.A. Sorensen, M. Cruz, W.T. Mito, Research evaluations of a lithium disilicate restorative system, Empress 2 Signature Int. 5 (1998) 4–10. [5] A.J.E. Qualtrough, V. Piddock, Dental ceramics: what's new? Dent. Update 29 (2002) 25–33. [6] C.F. Stappert, N. Stathopoulou, T. Gerds, J.R. Strub, Survival rate and fracture strength of maxillary incisors, restored with different kinds of full veneers, J. Oral Rehabil. 32 (2005) 266–272. [7] C.F. Stappert, W. Att, T. Gerds, J.R. Strub, Fracture resistance of different partialcoverage ceramic molar restorations, J. Am. Dent. Assoc. 137 (2006) 514–522. [8] C.F. Stappert, N. Denner, T. Gerds, J.R. Strub, Marginal adaptation of different types of all-ceramic partial coverage restorations after exposure to an artificial mouth, Br. Dent. J. 199 (2005) 779–783. [9] M.F. Ayad, N.Z. Fahmy, S.F. Rosenstiel, Effect of surface treatment on roughness and bond strength of a heat-pressed ceramic, J. Prosthet. Dent. 99 (2008) 123–130. [10] M. Ozcan, P.K. Vallittu, Effect of surface conditioning methods on the bond strength of luting cement to ceramics, Dent. Mater. 19 (2003) 725–731. [11] M. Ozcan, The use of chairside silica coating for different dental applications: a clinical report, J. Prosthet. Dent. 87 (2002) 469–472. [12] M.B. Blatz, A. Sadan, M. Kern, Resin-ceramic bonding: a review of the literature, J. Prosthet. Dent. 89 (2003) 268–274.
[13] G.A. Borges, A.M. Sophr, M.F. Goes, L.C. Sobrinho, C.N. Daniel, Effect of etching and airborne particle abrasion on the microstructure of different dental ceramics, J. Prosthet. Dent. 89 (2003) 479–488. [14] G. Saygılı, S. Şahmalı, Effect of ceramic surface treatment on the shear bond strengths of two resin luting agents to all-ceramic materials, J. Oral Rehabil. 30 (2003) 758–764. [15] H.R. Horn, Porcelain laminate veneers bonded to etched enamel, Dent. Clin. North Am. 27 (1983) 671–684. [16] A.H. Suliman, J.S. Edward, P. Jorge, Effect of surface treatment and bonding agents on bond strength of composite resin to porcelain, J. Prosthet. Dent. 70 (1993) 118–120. [17] M. Aida, T. Hayakawa, K. Mizukawa, Adhesion of composite to porcelain with various surface conditions, J. Prosthet. Dent. 73 (1995) 464–470. [18] A.M. Lacy, J. La Luz, L.G. Watanabe, M. Dellinges, Effect of porcelain surface treatment on the bond to composite, J. Prosthet. Dent. 60 (1988) 288–291. [19] A.N. Ozden, F. Akaltan, G. Can, Effect of surface treatments of porcelain on the shear bond strength of applied dual-cured cement, J. Prosthet. Dent. 72 (1994) 85–88. [20] K. Kamada, K. Yoshida, M. Atsuta, Effect of ceramic surface treatments on the bond of four resin luting agents to a ceramic material, J. Prosthet. Dent. 79 (1998) 508–513. [21] N. Madani, F.C.S. Chu, A.V. McDonald, R.J. Smales, Effects of surface treatments on shear bond strengths between a resin cement and an alumina core, J. Prosthet. Dent. 83 (2000) 644–647. [22] A. Della Bona, Characterizing ceramics and the interfacial adhesion to resin: II— the relationship of surface treatment, bond strength, interfacial toughness and fractography, J. Appl. Oral Sci. 13 (2005) 101–109. [23] H. Kato, H. Matsumura, M. Atsuta, Effect of etching and sandblasting on bond strength to sintered porcelain of unfilled resin, J. Oral Rehabil. 27 (2000) 103–110. [24] D. Sen, E. Poyrazoglu, B. Tuncelli, G. Goller, Shear bond strength of resin luting cement to glass-infiltrated porous aluminum oxide cores, J. Prosthet. Dent. 83 (2000) 210–215. [25] D.M. Wolf, J.M. Powres, K.L. O'Keefe, Bond strength of composite to etched and sandblasted porcelain, Am. J. Dent. 6 (1993) 155–158. [26] W.P. Kelsey, M.A. Latta, C.M. Stanislav, R.S. Shaddy, Comparison of composite resin-to-porcelain bond strength with three adhesives, Gen. Dent. 48 (2000) 418–421. [27] K.A. Kupiec, K.M. Wuertz, W.W. Barkmeier, T.M. Wilweding, Evaluation of porcelain surface treatment and agents for composite porcelain repair, J. Prosthet. Dent. 76 (1996) 119–124. [28] C.M. Kussano, G. Bonfante, J.G. Batista, J.H.N. Pinto, Evaluation of shear bond strength of composite to porcelain according to surface treatment, Braz. Dent. J. 14 (2003) 132–135. [29] T.H. Maiman, Stimulated optical radiation in ruby, Nature 187 (1960) 493. [30] L.J. Miserendino, The history and development of laser dentistry, in: L.J. Miserendino, R.M. Pick (Eds.), Laser in Dentistry, 1st ed., Quintessence Publishing Co.,Inc., Singapore, 1995, p. 17. [31] R.A. Convissar, E.E. Goldstein, A combined carbon dioxide/erbium laser for soft and hard tissue procedures, Dent. Today 20 (2001) 66–71. [32] E. Beyer, K. Behter, U. Petschke, Schweissen mit CO2-Lasern, Laser u Optoelektronik 18 (1986) 35–46.Misrendino LJ, Pick RM, editors. Lasers in dentistry. Chicago: Quintessence;. p. 231–245 [33] T. Akova, O. Yoldas, M.S. Toroglu, H. Uysal, Porcelain surface treatment by laser for bracket-porcelain bonding, Am. J. Orthod. Dentofacial Orthop. 128 (2005) 630–637. [34] J.W. Thurmond, W.W. Barkmeier, T.M. Wilwerding, Effect of porcelain surface treatments on bond strengths of composite resin bonded to porcelain, J. Prosthet. Dent. 72 (1994) 355–359. [35] I. Stangel, D. Nathanson, C.S. Hsu, Shear strength of the composite bond to etched porcelain, J. Dental Res. 66 (1987) 1460–1465. [36] A. Piwowarczyk, H.C. Hauer, J.A. Sorensen, In vitro shear bond strength of cementing agents to fixed prosthodontic restorative materials, J. Prosthet. Dent. 92 (2004) 265–273. [37] A. Della Bona, K.J. Anusavice, C. Shen, Microtensile strength of composite bonded to hot-pressed ceramics, J. Adhes. Dent. 2 (2000) 305–313.
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[38] M. Ozcan, H.N. Alkumru, D. Gemalmaz, The effect of surface treatment on the shear bond strength of luting cement to a glass-infiltrated alumina ceramic, Int. J. Prosthodont. 14 (2001) 335–339. [39] B. Gökçe, B. Ozpinar, M. Dündar, E. Cömlekoglu, B.H. Sen, M.A. Güngör, Bond strengths of all-ceramics: acid vs laser etching, Oper. Dent. 32 (2007) 173–178. [40] B. Kim, H.E.K. Bae, J.S. Shim, K.W. Lee, The influence of ceramic surface treatments on the tensile bond strength of composite resin to all-ceramic coping materials, J. Prosthet. Dent. 94 (2005) 357–362.
[41] E. Osorio, M. Toledano, B.L. Silveira, R. Osorio, Effect of different surface treatments on In-Ceram Alumina roughness. An AFM study, J Dent. 38 (2009) 118–122. [42] IPS e.max lithium disilicate; The future of all-ceramic dentistry. Ivoclar-Vivadent documentation, 2009.